Method of and apparatus for accurately mounting bits in engraving tools for electronic printing form engraving machines

ABSTRACT

A preground engraving tool bit is first accurately positioned relative to a mounting member, then secured to the mounting member for handling, and with the aid of the mounting member finally operationally united with a tool holder. All this is accomplished with extreme accuracy in a simple, efficient device especially devised for making such engraving tools for electronic printing form engraving machines.

United States Patent [191 Baar [111 3,815,217 I June 11, 1974 1 METHOD OF AND APPARATUS FOR ACCURATELY MOUNTING BITS IN ENGRAVING TOOLS FOR ELECTRONIC PRINTING FORM ENGRAVING MACHINES [75] Inventor: Walter Baar, Kiel, Germany [73] Assignee: Dr. Ing. Rudolf Hell GmbH [22] Filed: Mar. 16, 1973 {21] Appl. No.: 342,209

[30] Foreign Application Priority Data Mar. 22, 1972 Germany 2213768 [52] US. C1..... 29/464, 29/407, 33/1845, 269/7 [51] Int. Cl B231] 3/00 [58] Field of Search 33/1845, 184.6, 180 R,

33/180 X, 181 R, 181 X, 286; 269/7, 55, 57, 62; 29/464, 467, 468, 200 J, 200 P, 407

[56] References Cited UNITED STATES PATENTS 3,131,464 5/1964 Weigel 29/407 3,165,834 1/1965 BentOn 33/184.5 3,324,759 6/1967 Fielding 33/1845 3,578,868 5/1971 Wopkemeier et a1 33/185 R 3,600,815 8/1971 Link 33/185 R 3,642,269 2/1972 Ladd 269/62 3,651,401 3/1972 Cooney 269/57 Primary Examiner-Charles W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson 57] ABSTRACT A preground engraving tool bit is first accurately positioned relative to a mounting member, then secured to the mounting member for handling, and with the aid of the mounting member finally operationally united with a tool holder. All this is accomplished with extreme accuracy in a simple, efficient device especially devised for making such engraving tools for electronic printing form engraving machines.

14 Claims, 5 Drawing Figures This application relates to a method of and apparatus for accurately mounting bits in tool holders, and is more particularly concerned with producing engraving tools for electronic printing form engraving machines.

In the production of printing forms by means of engraving' machines the engraving tools are controlled electronically, that is, by electrical signals effected by electro-optic sensing of printing patterns in a dot-bydot and line-by-line according to a screen the pattern of which must be accurately reproduced on the printing form. Depending on the tone value detected during the sensing process, more or less material is engraved from the surface of a raw printing form by means of the engraving tool. The recesses produced in this way are called screen components or small dish recesses in the following description, and such recesses must be quite accurately arranged as to respective positions and must be quite accurately engraved with respect to their shapes, because the human reading eye will be bothered by irregularities in the printed material produced from printing forms in which the position and shape of the screen components or small dish recesses are inexact.

Especially in the engraving of photogravure printing cylinders where the volume of screen components or small dish recesses formed by the engraving tool determines the tone value recorded in the process, narrow lands must be maintained between the individual recesses for sliding of the doctor blades thereon after the inking process for removal of superfluous printing ink. Since as great a volume as possible must be engraved out of the recesses for effecting dark tones, only very narrow lands remain between such recesses. Therefore the exact shape and exact spacing of the recesses as determined by the control screen depends critically on the proper geometric shape of the cutting portion of the engraving-tool and on the exact spacial arrangement of the cutting portion with respect to the surface being engraved. v

Although development in engraving machines has provided for fairly accurate mounting of engraving tools and actuating apparatus therefore, no satisfactory method or means for producing the engraving tool itself, that is the unit consisting of cutting bit and holder for the cutting bit to attain the desired precision have heretofore been provided. Prior practice has involved attachment of the cutting bit, such as a desirable hard metal alloy or jewel material such as semi-precious jewel or diamond, in the holder and then grinding of the bit, as is common in the production of cutting tools for metal working and the like. However, due to the particular shape necessary in engraving tool holders, grinding of the bits affects the holder, and this makes it undesirable to bond the bit as a raw part into the holder and to then grind the bit, since the holder is ground away in the grinding of the bit.

An important object of the present invention is to overcome the foregoing and other disadvantages, deficiencies, inefficiencies, shortcomings and problems in prior methods and apparatus and to attain important improvements, advantages, and new and improved results in the mounting of cutting bits in engraving tool holders.

Another object of the invention is to provide a method of and means for the production of engraving tools for electro-mechanical engraving of printing forms attaining the required precision and thorough attachment of the cutting bit whereby to assure accuracy in the engraving of printing surface recesses.

A further object of the invention is to provide a new and improved method of and means for accurately and with precision uniting pre-ground cutting bits with holders in the production of engraving tools.

Yet another object of the invention is to provide a new and improved method of and-means for mounting engraving tool bits with holders in two steps attaining extreme accuracy.

Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

FIG. 1 is a schematic representation of a printing cylinder surface and an engraving tool to' show how such a tool operates in service.

FIG. 2 is an isometric view of a pre-ground cutting bit.

FIG. 3 is an isometric view of a device for attaching the cutting bit to an intermediate mounting member.

FIG. 4 is a perspective view of a device for effecting final mounting of the cutting bit with a tool holder.

FIG. 5 is a perspective view of a modified device for final reassemblying the cutting bit with the holder. By way of illustration a fragment of the surface of a printing cylinder 1 is illustrated in FIG. 1 and which during engraving rotates in the direction of the arrow 2 at a uniform circumferential speed. Printing ink receiving screen components or small dish recesses 3 are formed in the printing surface by an engraving tool bit 7 so positioned adjacent to the printing surface of the cylinder 1 that its cutting tip 5 will form the recesses 3 in controlled vibrating or oscillating movements of the tool as indicated by the directional arrow 4. It will be understood that the engraving tool 7 as schematically illustrated in FIG. 1 is mounted in a holder, to be hereinafter described, which is actuated in the desired oscillating movement by electrically controlled magnetic system. In a typical example, the engraving tip 7 penetrates the surface of the printing cylinder 1 approximately 4,000 times per second. In the relative rotation of the printing cylinder 1 the tip 7 will therefore follow a relative operating path generally indicated by the dash line 6.

On reference to FIG. 2 a more detailed illustration of the cutting bit 7 has been illustrated which, for example, may be prismatically ground diamond with its cutting tip 5 formed by faces bounded by edges 8, 9 and 10 and which are properly related to longitudinal reference surfaces of the bit identified as l2, l3, l4 and 15 for attaining the exact position of the bit in its holder. The bit 7 is secured in a holder at the reference surfaces 12, 13 and 14 and the tip 5 will remove material on penetrating the surface of the printingcylinder to produce the small dish shaped recesses 3. These small recesses 3 serve to receive the printing ink during the printing process and must be precisely formed such as to an exactness of approximately 1/2 micron in dimensions and in position with respect to the other recesses in order to obtain perfect printing reproduction. In spite of the tiny size of the cutting bit 7, precision is demanded with respect to its cutting tip 5, its mounting within the engraving system, and the operating stroke.

Accurate mounting of the cutting bit 7 in a tool holder is accomplished according to the present invention in two steps by first exactly orienting it with respect to an intermediate mounting member to which it is temporarily attached, and secondly with the aid of the intermediate mounting member assemblying the bit with a holder in a precise relation to unite the bit with the holder. Apparatus for the purpose is provided with precisely finished and related reference or guide sur faces to be engaged by the cutting bit in the course of effecting mounting thereof. To accomplish the first step in mounting the bit 7, a device 16 (FIG. 3) is provided. This device has reference or guide surfaces for the bit 7 comprising a flat surface 17 against which the longitudinal surface 12 of the bit is engaged in face-toface relation and with the cutting tip engaged firmly against a gauge surface 18 extending angularly relative to the surface 17 and joining the surface 17 at a reentrant angle joint 19. By thus positioning the bit 7, an intermediate mounting member 21 longitudinally shiftably guided in a groove 20 parallel to and spaced from the gauge surface 18 and the juncture 19 a proper distance is positioned for engagement with the bit in a manner to properly gauge the length to which the cutting tip 5 of the bit 7 should project from a tool holder with which the bit will ultimately be assembled. For engagment with the bit 7, the intermediate holder 21 has a contactsurface 22 at its front end which is-placed in face-to-face engagement with the proper longitudinal guide surface on the bit which is disposed angularly to the guide surface 17, herein the surface on the bit. The angle between the guide surface 22 and the guide surface 18 should be proper for the desired inclination of the longitudinal axis of the cutting bit with respect to the surface which must be engraved. In assemblying the bit 7 with the intermediate mounting mebmer surface 22, the surface 15 is pressed against the surface 22 with a suitable adhesive therebetween to hold the bit to the surface 22 against displacement while the second step in assembly with a tool holder is effected.

Although the second step, namely mounting of the bit 7 in a tool holder 26 (FIG. 4) can be effected as a sequential operation in a single device, for purpose of illustration a second device 23 has been illustrated for this purpose. To this end, the device 23 includes means in this instance comprising a block, similarly as the device 16 comprises a basic block, having a longitudinal groove or guideway 24 in which the elongated intermediate mounting member 21 is received, similarly as it is received in the groove of the device 16 accept in the device 23 the bit 7 as carried by the member 21has the tip 5 directed toward a surface 29 which corresponds substantially to the surface of a printing cylinder. Thus the surface 29 serves as a gauging surface to be sure that the bit tip 5 is accurately placed. In this instance, by shifting the holder 21 longitudinally in the guide groove 24, the bit 7 is placed into a mounting recess 27 provided therefore in one end of the holder 26. Correct positioning of the holder 26 with the recess 27 at the proper elevation above the surface 29 to receive the bit 7 is effect by supporting the holder fixedly upon a support 25 provided for this purpose on the device 23. Thereby, by axially shifting the intermediate mounting member 21 toward the rigidly supported holder 25, the cutting bit 7 is positioned correctlyin the recess 27. To assist in effecting this, suitable demarcation stops may be provided or a microscope 28 associated with the device 23 may be utilized for visually ascertaining that the assembled relationship uniting the bit with the holder is properly accomplished, in view of the small size of the parts.

' As assembled with the holder 26, the bit 7 is fixedly secured by suitable means such as soldering, sintering, bonding by means of cold or heat hardening plastic bonding adhesives, or other means or even clamping. This assures that the bit 7 will be held quite effectively against displacement relative to the holder 26 in-use, with the longitudinal surfaces 12, 13 and 14 of the bit engaged with opposing surfaces in the recess 27 of the holder. After the bit7 has been transferred to and secured in the holder 26, the intermediate mounting member 21 is released at its carrying surface 22 from the bit and the holder 26 is removed from the device 23 for mounting in an engraving machine.

In the engraving machine, a support for the holder 26 similar to the support 25 is provided but in which the holder support is oscillatable by means of an electrically controlled magnetic system. Thus, if one considers the surface 29 as representing the surface to be engraved and the holder 25 the oscillatory support for the holder 26 in the engraving machine it will be apparent how the tip 5 of the cutting bit 7 is caused to function in its engraving mode.

Instead of having the intermediate mounting member 21 reciprocably slidably mounted in a guide groove 24a (FIG. 5) in a body block of a device 23a, the arrangement may comprise having the mounting member 21 project to a fixed extent over the surface 29a and there hald against reciprocable movement as by means of pins 32 and 33. In this instance the holder 26 is supported by a fixed support 25a mounted on a reciprocably movable member 30 longitudinally slidably shiftable in a guide track 31 of the member 23a parallel with the groove 24a in which the intermediate mounting member 21 is mounted. For uniting the holder 26 with the bit 7, the carriage block 30 is shifted in its track 31 toward the intermediately supported bit 7 until the bit is received within the complementary recess 27 of the holder. Observation of the assembly operation in view of the tiny nature of the parts can be effected through the microscope 28a. If desired an index mark on the support 25a or a specially provided reference edge on the holder 26 may be provided on which the microscope can focus.

Inasmuch as the support 25 or 25a for the holder 26 is generally simulative of the corresponding support in the engraving machine in its neutral position, it will be appreciated that once the bit 7 has been mounted in the holder 26 pursuant to the present method and with the aid of the present apparatus, a high order of efficiency, accuracy and maximum utility are provided in the engraving tool unit. By the grinding and gauging of the bit during the assembly steps proper cutting tip length projecting of the bit beyond first the intermediate holder 21 and then beyond the supporting portion of the holder 26 are attained.

I claim as my invention:

l. A method of making a printing form engraving tool having a cutting bit united with a tool holder, comprismg;

supporting a cutting bit in a position wherein a longitudinal surface thereof faces toward an intermediate mounting member;

placing a carrying surface of the intermediate mounting member in face-to-face abutment with said longitudinal surface of the bit;

temporarily attaching said surfaces so that the bit is carried by saidintermediate mounting member;

relatively moving said mounting member and said holder and assemblying said bit in a complementary recess in said holder; and

then separating said intermediate mounting member from said bit at said surfaces.

2. A method according to claim 1, including supporting said bit on a surface thereof angular to said longitudinal surface lying aginst a guide surface and with a cutting tip on said bit engaging a gauging surface angular to said supporting surface, and moving said intermediate mounting member along said supporting surface to effect said abutment of said carrying surface and ,said longitudinal surface.

3. A method according to claim 2, including moving said intermediate mounting member in a guide groove and thereby guiding the member along said guide surface toward said bit.

4. A method according to claim 1, including effecting said temporary attachment of the bit to said intermediate mounting member in a manner to leave a substantial cutting tip length of the bit projecting beyond the member, and effecting the assemblying of the bit in the recess of the holder in a manner to leave a substantial cutting tip length of the bit projecting beyond the holder.

5. A method according to claim 1, comprising holding the tool holder stationary and moving the intermediate mounting member to assemble the bit in said complementary recess.

6. A method according to claim 1, comprising the holding said intermediate mounting member stationary and moving said holder to receive said bit in said complementary recess.

7. A method according to claim 1, comprising facing three angularly related longitudinal surfaces of said bit in face-to-face abutment with three complementary surfaces in said recess, and fixedly securing the bit in said recess.

that the bit is then carried by said mounting memher; and

means for supporting a tool holder in position to receive said bit in a complementary recess in the tool holder by relative movement of the tool holder and the mounting member.

9. Apparatus according to claim 8, said supporting means for the cutting bit comprising a guide surface for supporting one side of the bit and a gauging surface located angular to the guiding surface.

10. Apparatus according to claim 9, said mounting member being elongated, and said supporting means therefor comprising a groove in which the member is guidedly received and from which the member projects to move slidably along said guide surface toward engagement of said carrying surface with said longitudinal surface of the bit. 7

11. Apparatus according to claim 8, said member being related on its supporting means relative to said bit to leave a substantial cutting tip length of the bit free'to project beyond the member in the assembled relation of the bit with the member.

12. Apparatus according to claim 8, including means for holding the holder in a fixed position and said mounting member being mounted for movement toward the holder to insert the bit in the complementary recess of the holder.

13. Apparatus according to claim 8, including means for holding the mounting member stationary relative to the holder, and means for moving the holder toward the bit carried by the member for receiving the bit in said recess of the holder.

14. Apparatus according to claim 8, including means for observing accuracy of assembly of the bit with the holder. 

1. A method of making a printing form engraving tool having a cutting bit united with a tool holder, comprising; supporting a cutting bit in a position wherein a longitudinal surface thereof faces toward an intermediate mounting member; placing a carrying surface of the intermediate mounting member in face-to-face abutment with said longitudinal surface of the bit; temporarily attaching said surfaces so that the bit is carried by said intermediate mounting member; relatively moving said mounting member and said holder and assemblying said bit in a complementary recess in said holder; and then separating said intermediate mounting member from said bit at said surfaces.
 2. A method according to claim 1, including supporting said bit on a surface thereof angular to said longitudinal surface lying aginst a guide surface and with a cutting tip on said bit engaging a gauging surface angular to said supporting surface, and moving said inteRmediate mounting member along said supporting surface to effect said abutment of said carrying surface and said longitudinal surface.
 3. A method according to claim 2, including moving said intermediate mounting member in a guide groove and thereby guiding the member along said guide surface toward said bit.
 4. A method according to claim 1, including effecting said temporary attachment of the bit to said intermediate mounting member in a manner to leave a substantial cutting tip length of the bit projecting beyond the member, and effecting the assemblying of the bit in the recess of the holder in a manner to leave a substantial cutting tip length of the bit projecting beyond the holder.
 5. A method according to claim 1, comprising holding the tool holder stationary and moving the intermediate mounting member to assemble the bit in said complementary recess.
 6. A method according to claim 1, comprising the holding said intermediate mounting member stationary and moving said holder to receive said bit in said complementary recess.
 7. A method according to claim 1, comprising facing three angularly related longitudinal surfaces of said bit in face-to-face abutment with three complementary surfaces in said recess, and fixedly securing the bit in said recess.
 8. Apparatus for making an engraving tool having a cutting tip united with a tool holder, comprising: an intermediate mounting member; means for supporting the mounting member; means for supporting a cutting tip in a position with a longitudinal surface thereof facing toward the mounting member; the mounting member having a carrying surface facing toward said bit surface; said mounting member and said bit as supported by the respective supporting means being relatively movable to place said surfaces in face-to-face abutment for temporary attachment of the surfaces so that the bit is then carried by said mounting member; and means for supporting a tool holder in position to receive said bit in a complementary recess in the tool holder by relative movement of the tool holder and the mounting member.
 9. Apparatus according to claim 8, said supporting means for the cutting bit comprising a guide surface for supporting one side of the bit and a gauging surface located angular to the guiding surface.
 10. Apparatus according to claim 9, said mounting member being elongated, and said supporting means therefor comprising a groove in which the member is guidedly received and from which the member projects to move slidably along said guide surface toward engagement of said carrying surface with said longitudinal surface of the bit.
 11. Apparatus according to claim 8, said member being related on its supporting means relative to said bit to leave a substantial cutting tip length of the bit free to project beyond the member in the assembled relation of the bit with the member.
 12. Apparatus according to claim 8, including means for holding the holder in a fixed position and said mounting member being mounted for movement toward the holder to insert the bit in the complementary recess of the holder.
 13. Apparatus according to claim 8, including means for holding the mounting member stationary relative to the holder, and means for moving the holder toward the bit carried by the member for receiving the bit in said recess of the holder.
 14. Apparatus according to claim 8, including means for observing accuracy of assembly of the bit with the holder. 